Low Labor Requirements Research Articles

Application of the agar gel precipitin test to detect antibodies to Salmonella enterica serovar enteritidis in serum and egg yolks from infected hens

Serological surveillance can be an important component for egg quality assurance programs geared toward controlling problems with Salmonella enterica serovar Enteritidis (S. enteritidis) within a flock. Serum is the primary sample source for the procedures, although egg yolk antibody assays have become popularity in recent years. However, these assays tend to be labor intensive, requiring procedures for extracting antibodies from the yolk followed by assaying the samples. We describe an adaptation of the agar gel precipitin (AGP) test for use in detecting antibodies to S. enteritidis deposited in egg yolks of infected hens. Yolk or sera from infected birds were administered to wells cut into seven-well clusters in an agar gel plate, and detection antigen was added to the center well. The agar gels were incubated for 24 h and then examined for the presence of precipitin lines formed by the interaction of antibody with antigen. Three different antigens were tested: S. enteritidis flagella, SEF14 (a 14-kDa fimbrial protein produced ostensibly by S. enteritidis), and a sodium deoxycholate extract of whole S. enteritidis organism. Flagella and the organism extract detected antibodies to S. enteritidis in the yolk and sera, whereas SEF14 was not reactive. Positive reactions were observed in serum 1 wk postchallenge, whereas in yolks, this was further delayed by 1 wk. The sensitivity of the test was slightly less than the standard microagglutination assay, although specificity was slightly higher, as indicated by results from sera and yolks from birds infected with Salmonella enterica serovar Typhimurium. Simplicity and low labor requirements of the assay would allow for the potential testing of several hundred egg samples within a day, which would make up for test shortcomings due to sensitivity. The AGP test could be an important tool for individuals using serological testing to monitor the S. enteritidis situation within their flocks or as a rapid screen for vaccine responses. The assay could also be used in tandem with other AGP tests to screen for the presence of multiple avian pathogens.

Environment, Production and Social Difference in the Kalahari Thornveld, c1750–1830

This article considers the food production activities of people in the Thlaping and Tlharo chiefdoms in the present-day Northern Cape and North-West Provinces between c1750 and 1830. It considers food production methods, their environmental suitability and how food produtction related to social difference. It is arguted that the Tlhaping and Tlharo chiefdoms did not arise through the migration of agro-pastoralists, but that indigenous inihabitants began stock keeping and cultivating as the chiefdoms were established in the mid-eighteenth century. Thereafter food production remained extensive and the products of pastoralism – milk – provided the staple of the diet. Food production did not provide support for all people, and a significant class of foragers, who were not ethnically differentiated from other members of the chiefdons, lived at the bottom of the society and outside of the towns. It was possible for men to move between stock keeping and foraging in a process similar to the “ecological cycle” described by Richard Elphick for the Khoisan. However, chiefs and headmen exerted their power, in part gained through stock ownership, to protect their positions of wealth fromn the vagaries of nature and human competition. Agriculture was the most intensive use of the environmnent and supplemented food gained through pastoralism and foraging, rather than providing the staple. Production methods show it had relatively low labour requirements and may be understood as shifting cultivation. It was the responsibility of women, who could not achieve status through their production. Cultivation was a less individualistic activity than pastoralism, but its reciprocity did not amount to communalism. A consideration of production activities and yields in this enviroinment suggests that men invested their hopes for wealth in stock rather than in women’s labolur power; that success as stock keepers was not an option for all men, and that the exclusion of women from stock ownership was due to cultural forces and not a means of relegating them to service as agricultural labourers.

Autotrophic Denitrification with Elemental Sulphur in Small-Scale Wastewater Treatment Facilities

An autotrophic denitrification process with elemental sulphur to achieve a high quality effluent with a low concentration of total N was tested at laboratory scale. Two types of wastewater were tested during a period of 10 months. One was a multiple household wastewater obtained from a municipal wastewater treatment plant and the other was a single household wastewater collected from a family. The wastewaters were first treated by primary sedimentation, followed by nitrifying trickling filtration. The nitrified effluents from the trickling filter were further denitrified in an autotrophic denitrification stage. The autotrophic denitrifying reactor was filled with a mixture of elemental sulphur powder and small pieces of limestone. Sulphur was used as an electron donor and CaCO3 in the limestone served as pH buffer. With a hydraulic retention time of 2–3 hours, up to 86 % of total oxidizable nitrogen (TON) was removed from the multiple household wastewater and 75 % from the single household wastewater. The total N concentration in the final effluents was 3 mg l−1 for the multiple household wastewater and 17 mg l−1 for the single household wastewater. Besides the high removal efficiency and the short hydraulic retention time, other advantages were also noted such as no specific need for inoculum, rapid start up, a wide temperature range for application and low technical labour requirement. Hence, autotrophic denitrification offers interesting potential for removing surplus nitrate from nitrified domestic wastewater particularly in small-scale wastewater treatment facilities.

Anode effects in electrowinning

In traditional electrowinning operations, metal particles from commercial insoluble anodes flake off the immersed surfaces under high current densities and thus become occluded on the adjacent cathode surface thereby impairing the cathode product quality and market grade. This results in an undersirable physical appearance of the cathode due to irregular protrusions which impede subsequent material handling operations such as packaging, weighing and shipping. The paper serves to highlight the existing problems inherent with permanent anodes and suggests possible areas for further research and development studies. At present, permanent anodes are employed in the worldwide electrolytic industry for the recovery of base metals such as copper, nickel, cobalt, and zinc while smaller scale operations exist to recover precious metals such as gold and silver from leach solutions. The coupling of solvent extraction with electrowinning technology (SX-EW) is now a widespread practice. Unfortunately, the usage of permanent anodes has the disadvantages of ongoing maintenance costs to clean the anode surfaces and refurbish the wetted area, results in lower anode useful life, the expense of anode replacement, lower current efficiency, higher power consumption as compared to electrorefining, and inferior cathode quality which becomes contaminated due to deterioration of the metal or metal alloy used to fabricate the insoluble anodes. Apart from improvements in productivity and cathode product quality, and lower labour requirements, the driving force to remedy present electrowinning performance is mainly a reduction in energy. Another associated problem area is the usage of mother blanks fabricated from either aluminum, copper, titanium, or stainless steel as employed to enable full deposit stripping. It is recognized that the construction of the different hanger bars used to support both permanent anodes and mother blanks presents another problem area for study which is addressed within the paper. The writers advocate investigations to improve non-ferrous metal stripping practice, increase current efficiency and extend the useful life of permanent electrodes. The anticipated improvement in full plate cathode chemical and physical quality will benefit downstream operations such as copper wirerod production and subsequent fine wire drawing.

Capability and Cost of Treatment Technologies for Small Systems

Treatment technologies for small systems should have low construction and operating costs, simple operation, low maintenance, and low labor requirements. Processes that meet some or all of these conditions are coagulation‐filtration package plants, diatomaceous earth filtration, slow sand filtration, ion exchange, granular activated carbon, and air stripping. Reverse osmosis, lime softening, and activated alumina may also be used. All of these processes are evaluated based on capability and cost.

Comparison of Melengestrol Acetate-Prostaglandin F 2α to Syncro-Mate B for estrus synchronization in beef heifers

Three hundred and ten yearling heifers of various breeds were used in five trials to compare two estrus synchronization treatments. Treatment 1 consisted of Melengestrol Acetate-Prostaglandin F 2α (MGA-PGF 2α). Heifers were fed 0.5 mg MGA/head/d for 14 to 16 d. Sixteen or 17 d after the final MGA feeding, heifers were injected i.m. with 25 mg PGF 2α. Treatment 2 consisted of Syncro-Mate B (SMB). Heifers were given a 9-d norgestomet implant plus an injection containing 3 mg norgestomet and 5 mg estradiol valerate i.m. at implant insertion. Heifers were observed for estrus at 6-h intervals for 120 h after the end of treatments and were artificially inseminated 12 to 18 h after observed estrus. Heifers synchronized with MGA-PGF 2α and SMB had a similar (P > 0.10) estrous response (83.4 vs 90.2%) and a similar (P > 0.10) degree of synchrony (71.8 vs 79.0%) following treatment. However, the synchronized conception rate (68.7 vs 40.6%) and the synchronized pregnancy rate (57.3 vs 36.6%) were higher (P < 0.01) in MGA-PGF 2α than SMB heifers. Breeding season pregnancy rates were similar in both treatment groups. Heifers in both groups that were classified as cycling prior to initiation of treatment had improved reproductive performance following synchronization compared with those classified as noncycling. Based on higher synchronized conception and pregnancy rates and lower labor requirements and drug costs, the MGA-PGF 2α system appears to be a better method to synchronize estrus in beef heifers than the SMB system.

Costs of Milk Harvest in Dairy Cattle: Implications for Direct Selection and Cow Culling

Labor and machine costs of milking were derived from data on Holstein and Jersey cows to determine their importance for direct selection and culling. The labor cost of milking Holsteins ranged from $.16 to $.27/day for milk yields when labor was valued at $4.50/h. Machine stripping comprised about one-third of this labor cost. Effects of lactation number for labor and machine costs were small, $.05 and $.02/day, for cows of same yield and stage of lactation. Standard deviations of labor and machine costs of milking Holstein cows were $13.39 and $7.25/305-day lactation. Variation in labor or machine costs was insufficient to warrant direct selection for improved economy of milking. Parity of cow could contribute to a decision to cull in extreme cases of low production and high labor and/or machine requirements but is otherwise inconsequential.

An Evaluation of Individual Outdoor Houses and Enclosed Confinement Buildings as Farrowing Systems for Swine

This study was conducted during March and April, 1970 to evaluate the performance, economics and management of farrowing 117 litters in the following facilities: (1) An enclosed confinement building with 48 farrowing crates on a solid concrete floor. The sows were fed on a feeding platform twice daily. (2) An enclosed confinement building with 22 farrowing stalls on a solid concrete floor and a slotted floor pen located behind each farrowing stall. (3) Forty-seven individual outdoor houses located side by side in two rows facing the south with a pen in front of each house. The sows in facilities 2 and 3 were hand fed twice daily. The age of the litters when removed from each facility differed considerably as attributed to the design and intended use of each facility and the existing management program. Baby pig mortality was similar (9 to 11%) for all three farrowing systems. Litter weight was related to the age of the pigs when removed from the farrowing facilities. However, creep feed was provided in facility 2, but not facilities 1 and 3. The average daily temperature and relative humidity were similar in facilities 1 and 2 which maintained a more uniform environment with considerably less diurnal variation compared to the outdoor weather. The temperature and humidity in the individual houses varied with the outdoor conditions. The daily labor required per sow and litter was approximately six to seven times greater for facility 1 compared to facilities 2 and 3, respectively. The low labor requirement for facility 3 may be attributed in part to the mild climatic conditions at the time this experiment was conducted. Total variable costs per sow and litter were higher for facility 2, mainly due to the longer time the sows and litters were in the facility which increased the sow and creep feed cost. However, total variable costs to produce 99.0 lb. (45.0 kg) of pork were the lowest for facility 2 followed by facilities 3 and 1. Total fixed costs per sow and litter (based on maximum utilization of each facility) and total production costs (variable plus fixed cost) were considerably higher for facility 2 compared to facility 1 and the low cost for facility 3. The results of this study clearly indicate that the enclosed confinement building with a solid concrete floor was the least economical farrowing system, primarily due to the large amount of labor required daily in relation to the investment costs. In contrast, the enclosed confinement building where sows were fed in the farrowing stalls and the pen floor was slotted to eliminate daily cleaning was an economical long term investment, mainly due to the lower labor costs. However, the individual outdoor houses had the lowest daily labor requirement per sow and litter, the lowest investment cost and the lowest total production cost per sow and litter. The individual outdoor houses would be the most profitable farrowing facility where climatic and economic conditions do not differ greatly from those inherent in this study. The individual houses would be attractive to swine producers with limited capital and a need for flexibility.

Mathematical Techniques for Evaluating Labor Utilization in Dairy Plant Operations

Summary A comprehensive study of labor utilization was made in a commercial dairy plant. An attempt was made to correlate certain types of plant labor with total volume, e.g., processing variable and fixed and delay time; shipping, and cold storage time; and total time. The labor utilization data on an actual operation can serve as a guide in making comparisons with hypothetical plant studies. The data collected on labor utilization in a commercial plant study were treated statistically. The standard errors were found for the fixed times. An analysis of covariance was carried out on the labor used in each of the individual products, testing both the variable and fixed times for differences in labor used between days and between weeks and for significance of the regression coefficients. A regression equation was computed for each operation and the standard error of b was given. The results from the commercial plant study showed that only a few products exhibited significant day-to-day differences in labor used; whereas, weekly differences showed up in about one-third of the products. The regression coefficients were highly significant in most of the products, indicating that the labor used varied with a change in volume. An illustration was given to demonstrate the use of the equations as a management control on the plant labor used in a commercial dairy plant. The importance of volume in an actual operating dairy plant in effecting a relatively low labor requirement per unit was pointed out. The results from the volume-labor analysis were in agreement with hypothetical plant studies concerning economics of scale that are found in the literature, i.e., as the total volume increases within a plant operation, the amount of labor used per unit will usually decrease. Also, the use of the mathematical equations was illustrated in some plant situations to show how they might be used for determining the labor used.